Deltas under threat

  • 2015•10•12

    Mekong Delta

    Photo by Zita Sebesvari

    Ancient civilizations thrived along deltas such as those of the Nile and the Tigris-Euphrates rivers. Their fertile soil and dense river system have made them popular places for people to settle. Today deltas cover 1% of the earth but are home to more than 500 million people. Their diverse and rich ecosystems support agriculture, fisheries, and forest production, as well as major urban centers and harbors. Today, these deltas that have sustained mankind for centuries are under threat.

    UNU-EHS senior researcher Dr. Zita Sebesvari says, “Delta’s are densely populated low-lying areas that are often experiencing rapid socio-economic developments. They are also highly susceptible to climate change impacts such as sea level rise, salinity intrusion as well as more extreme flooding and cyclones.” In fact, most deltas lie just 5 meters above mean sea level. At the same time, 24 of the world’s major deltas are subsiding, some as much as 10 cm a year, due to compaction, up-stream dam construction as well as water and mineral extraction.

    What is a Delta and how are they formed?

    A river delta occurs where the river flows into the ocean or other large body of water. As rivers reach flatter terrain, the flow of water slows allowing for the deposition of sediments. These deposits build up over time. Eventually the water becomes shallower and land begins to rise above the water. This new-formed land is a river delta.

    Since deltas are created by the slow deposit of sediments, most deltas are very low-lying and only elevated just above sea level. This explains why up-stream dams that trap sediments also slowly starve deltas. Up-stream dams along with sea-level rise make deltas increasingly vulnerable to flooding. Recent assessments suggest that the portion of world deltas vulnerable to flooding could increase by 50 per cent.

    Measuring a delta’s vulnerability

    Researchers in the Environmental Vulnerability and Ecosystem Services (EVES) section at UNU-EHS are currently developing a Global Delta Vulnerability Index as part of the Belmont Forum funded DELTAS project. By examining three of the world’s largest deltas, the Amazon, Ganges-Brahmaputra and Mekong deltas, they hope to create a set of indicators that can assess how vulnerable a delta´s social-ecological systems are to natural hazards such as sea-level rise, salinity intrusion, flooding, cyclones, and pollution.

    To fix something you need to know what is broken. By providing a straightforward and effective way to assess a delta’s vulnerabilities, this Index can guide sustainable management of resources and the policies that need to be enacted to facilitate this. This will be crucial to ensure not only the safety of those living in deltas but also the health and resilience of the delta ecosystem as a whole.

    Through regional consultations with scientists and agency representatives from relevant sectors in Ho Chi Minh City (Viet Nam), Dhaka (Bangladesh), and Belém (Brazil), a set of indicators was developed and will be released in December 2015. These indicators will include both ecological and social indicators, including indicators related to biodiversity, water availability, demographic and economic characteristics.

    Coastal adaptation in the Mekong and Red River delta in Viet Nam

    The Mekong and Red River Delta regions, considered to be among the most vulnerable deltas to climate change globally, are experiencing higher levels of salinity in water and soil due to intrusion of saline water from the sea. In a region that depends on agricultural production, this can be devastating for local farmers. In the DeltAdapt project, over 20 scientists from Germany and Viet Nam are exploring how people living in the deltas are adapting to salinity intrusion.

    Land use changes very dynamically in these deltas. Some farmers switched from rice cultivation to shrimp farming while in other regions of the delta, farmers hope to find ways to keep or even return to rice production. Nguyen Minh Tu, one of the researchers in the DeltAdapt project and a PhD student at UNU-EHS, is trying to find out why. Whether it is due to salinity intrusion or changing markets and policies, understanding why people are switching agricultural systems can lead to more appropriate measures to ensure sustainable agricultural development in the deltas in the long run.

    For the next six months, Mr. Minh Tu will be conducting his PhD field work in the Mekong and Red River deltas. He was born and raised in the Mekong Delta region and says that , “The research is really meaningful for me not only to explore the phenomenon which is common in the delta where I  grew up, but also a great chance for me to develop my personal and professional career goals.

    UNU-EHS researchers are also leading two more work packages in the DeltAdapt project. Ms. Gianna Brown is currently also in the Mekong and Red River delta region exploring pollution patterns and how the concentration of pesticides and antibiotics have changed due to increasing salinity intrusion as well as to current land use changes. Ms. Pham Thi Thanh Hoai is also in the region investigating how farmer’s livelihoods have been influenced by increasing salinity and how local adaptation to salinity intrusion actually works in the context of dynamic environmental and socio-economic changes.

    The DELTAS and DeltAdapt project are the result of the EVES and VARMAP section’s long-term research presence in delta environments.